1. Field of the Invention
The present invention relates to a coupling structure for a pipe end, and in particular to a coupling structure for a pipe having concave sections and convex sections alternately in an axial direction disposed on at least one side of an inner circumference and an outer circumference.
2. Description of the Related Art
For an engine of, for example, four-wheel work vehicles an air intake duct is employed to connect between an air intake case of a carburetor and an air cleaner, the air intake duct being fabricated from a flexible bellows-type pipe for free arrangement within an engine room.
As shown in FIG. 5, the bellows-type pipe 10 is fabricated into a form having helical corrugations 14, 15, 16, 17 on an outer circumference and an inner circumference and a helical core 18 is disposed at the bottoms of the concave sections 16 of the inner circumference.
Heretofore, for joining the air intake duct comprising the bellows-type pipe 10 to a receiving part of the air cleaner and the like, a rubber seal 51 is fit around the outer circumference of a pipe 11 on the side of the receiving part, the bellows-type pipe 10 is fit over an outer circumference of the seal 51, and then a clamp 50 is mounted to fasten the bellows-type pipe 10 from its outer circumference.
According to the prior art as shown in FIG. 5, since the outer circumference of the bellows-type pipe 10 is directly pressed by the clamp 50, a stable sealing property is difficult to secure. Also, because of the helically wound core 18, an end face of the bellows-type pipe 10 becomes uneven and a part of the end face of the bellows-type pipe 10 projects outwardly (for example, refer to a projection 10A in FIG. 2). As above described, the construction as shown in FIG. 5 exposes the end face of the bellows-type pipe 10 resulting in deterioration of an esthetic view.
On the other hand, JP-A-2000-74281 discloses a coupling structure for use with a pipe provided with helical corrugations on an outer circumference of the pipe. According to this art, a tubular nipple is fit onto an inner circumference of the pipe, an elastic packing having helical corrugations on its inner circumference is fit about the outer circumference of the pipe, and then a holder is mounted to fasten from the outer circumference of the elastic packing.
The art as disclosed in JP-A-2000-74281 may be useful in its own way with respect to a pipe having a smooth tubular inner circumference, however, cannot be applied to a so-called bellows-type pipe having corrugations both on the inner and the outer circumferences.